1. Field of the Invention.
This invention relates to electrical terminal pins for use in interconnecting electrical leads, plated through holes in printed circuit boards and/or connector contacts and, in particular, to electrical terminal pin tips on insertion ends of the pins.
2. Description of Related Art.
It is well known in the connector art to use electrical pins to interconnect electrical leads, plated through holes in printed circuit boards and/or connector contacts. Such pins typically have square or round cross sections perpendicular to their longitudinal axes.
The pins are made from an electrically conductive material, such as copper, brass, phosphor bronze, beryllium copper or the like. It is further known to plate or coat the pins with a conductive layer, such as tin, nickel, pladium, gold, silver or a suitable alloy. Pins are plated in order to apply a layer on a pin core that does not oxidize as much as the material of the core. Less oxidation at an electrical connection improves electrical performance. Pins are made with a core material different than the plating material in order to reduce the cost of the pin and/or to make the pin more rigid than if the pin was entirely made out of the plating material.
It is well known in the art to make pin tips with flat tapered sides to facilitate alignment with and/or insertion into a plated through hole or a mating contact. For instance, FIG. 1 shows an enlarged perspective view of an electrical terminal pin tip 2 of a prior art electrical terminal pin 4 with a portion broken away to show a cross section 6 of the pin 4. The pin 4 comprises an electrically conductive inner core 8 plated with an electrically conductive outer layer 10. FIG. 2 is an end view of the prior art electrical pin tip 2 of FIG. 1.
Referring to FIGS. 1 and 2, the pin tip 2 has a pair of opposed flat swaged plated sides 12 that taper or slope towards a longitudinal axis of the pin 4 as the pin 4 approaches its longitundinal end. The pin tip 2 further has a pair of opposed flat trimmed non-plated sides 14 that taper or slope towards the longitudinal axis of the pin 4 as the pin 4 approaches its longitundinal end. The opposed flat trimmed non-plated sides 14 are jointed at the longitudinal end by a trimmed non-plated curved or cylindrical surface 16. When this tip 2 is inserted into a plated through hole or a female contact, the plated through hole or the female contact can slide against the non-plated tapered sides 14 causing some of the core material to be transferred onto the plated through hole or the female contact. Multiple insertions and withdrawals of the pin 4 into plated through holes or mating female contacts increase the probability of rubbing some of the core material off the non-plated sides 14 onto the plated through holes or mating female contacts. This transferred core material can ultimately be dragged or positioned between the pin plating 10 and the plated through hole or the female contact. Depending on the materials used for the core 8 and the plating or layer 10, this may increase the oxidation rate of the connection between the pin 4 and the plated through hole or the female contact, compared to a connection directly between pin plating 10 and the plated through hole or the female contact.
Other pin tips are shaped by trimming which removes plating material from trimmed flat sides. Then one or more additional process step is performed to plate the trimmed sides. Although this ensures that all exterior sides and surfaces of the pin tip are plated, it adds time and cost to the manufacturing process.
It is typical to simultaneously insert a plurality of pins, such as, mounted in a connector housing, into a mating set of plated through holes or female terminals. The insertion force required increases with the number of pins being inserted and can be significant. Tapered flat sides on pin tips reduce the inserion force required. However, it is desireable to further reduce the longitudinal insertion force without reducing the lateral retention force applied on the pin by the plated through holes or female terminals.
It is desirable to provide a pin tip that satifies the above described needs and overcomes the above described disadvantages of the prior art.